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My lenses for handheld NV at 1x, 2x, 3x

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#1 The Ardent

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Posted 16 July 2018 - 06:07 PM

Here is a explanation of my current lens system for handheld Night Vision viewing. 

 

The NVD (night vision device) normally comes with a c-mount lens for 1x viewing. From reading here this lens has a focal length ~ 26mm. 

 

1x is good for viewing the sky, but we astronomers want a closer view. To accomplish this we use longer focal length lenses. For every extra 26mm, we gain another integral step in magnification (approximately -which is good enough for a hobbyist) 

 

Lens focal length / magnification with NV

26mm / 1x 

50mm / 2x

75mm / 3x 

100mm/ 4x 

 

Based on experience with 135mm and 200mm lenses, I don't recommend going over 4x. It's just like handheld binoculars, more magnification = more handheld shakes. For the range of 5x and above, I recommend a small mounted telescope. Afocal with a 55mm Plossl can get down into this low range, depending on the scope. Search afocal night vision for details. 

 

In the general consumer market there are basically two types of lenses available : c-mount and other mount. 

 

C-mount lenses are made in a bewildering array of sizes, formats, and prices. The lens shown here is a Tamron 23FM25SP, described in this thread https://www.cloudyni...ing-on-nv-mod3/

 

This lens provides a decent image at a decent price. The most important feature to me is the 30.5mm filter thread , which allows direct coupling to the TNVC afocal adapter. This thread size is uncommon in c-mount lenses. 

For 1x viewing I used a RAF Camera 1.2 inch - 32tpi (ENVIS lens) to 1.25 inch astro filter (M28.5x0.6) adapter 

 

https://www.rafcamer...s-to-astro-1-25

 

to hold a  filter  in front of the Tamron. 

 

eBay has plenty of 30.5 mm cheap infrared filters available. 

 

For or non C-mount lenses there are several things to consider: Is a c-mount adapter available? What is the front filter thread size? Will it work with NV? 

 

The non-C mount  lenses I have are Canon FD mount film SLR lenses. These are old lenses only available secondhand. I'm very pleased with the performance of the two shown here. No vignetting and sharp to about 97% FOV (my estimate only)  I tried some zoom lenses that were not so good. The zooms lost about two magnitudes of stars and had more distortions. 

 

To use these lenses a C-mount to FD mount adapter is required. These are widely available on Amazon, EBay, and camera stores for all the common brand lenses. Check to make sure allows infinity focus. 

 

To to keep things simple I only use Canon FD mount lenses with a 55mm front filter. The front filter threads come in a variety of sizes. There are plenty of adapters out there, but for consistency I chose 55mm only. I have two 55 to 48mm step down rings to use 2" filters. I also have a couple of 55mm infrared filters. 

 

I just ordered a 55mm to 30.5 mm step down ring ($3) to attempt afocal with the Canon lenses. We'll see how that works. 

 

 

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#2 The Ardent

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Posted 16 July 2018 - 06:09 PM

The filter rings and filters, and another view of the parts.

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#3 The Ardent

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Posted 16 July 2018 - 06:13 PM

Comparison of the Tamron C-mount and Canon lenses

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#4 TOMDEY

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Posted 16 July 2018 - 06:59 PM

Hi, Ardent; Thanks! I got the 3x afocal that goes right over the (good!) stock 1x objective that came with the NV. Have you tried that? I'm wondering what might be better or worse. It seems to me that something designed and built for NV spectrum and sensor format... should be the most performance for the $$$.  Thanks!  Tom



#5 The Ardent

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Posted 16 July 2018 - 07:03 PM

Tom
I tried that lens , or one like it.

I preferred the Canon 85mm f/1.8 that I have. Just my $0.02

#6 Jeff Morgan

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Posted 16 July 2018 - 07:17 PM

Nice write-up Ray!

 

I love using SLR lenses with my Mod 3c. Currently I have a 50mm f/1.4 and 135mm f/2.8 (both Canon). I'll acquire two more, a 85mm and either the 200mm or possibly the Nikon 180 ED that Eddgie raves about. 

 

When I use these I think more in terms of Framing than Magnification, but regarding magnification we run into the same problems as conventional binocular users have: Holding the lens steady to realize the fine detail, and ergonomics (neck craning).

 

It seemed to me that exploring Binocular Mount solutions would be the way to go. I tried the Manfrotto Magic Arm and a Universal Astronomics Uni. Personal preference and taste figure largely in a solution and while these could be good for many, I was not happy with them.

 

So, I decided to duplicate the old TriCo Machine SkyWindow product I used to own:

 

5712789-Fuji 10x50 Sky Window.jpg

 

Nothing could touch it for ergonomics, portability, or stability.

 

It's downsides were dew potential (easy to combat), mirror reversed image (minor to me, and SkySafari can reverse the map), and mirror quality.

 

The base mirror was fine at 7x but naturally people wanted to put 12, 15, and 22x binos on them and the float glass mirrors were not up to that standard.

 

But for NV work 7x would probably never be exceeded because as you point out that is approaching the cross-over point to a telescope solution.

 

So, I ordered this first-surface mirror on ebay:https://www.ebay.com...ra/273325344735

 

The mirror tips for altitude, and it will use a Dob-style azimuth rotation. I'll use the Losmandy Dovetail Camera mount (DVCM) on a 8" D Plate, using that travel range to adjust for lens length. Aiming will be accomplished with a green laser mounted parallel to the optic.

 

Once I get the parts in, should only take an afternoon to cobble it together.

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#7 The Ardent

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Posted 16 July 2018 - 07:19 PM

Please see GG’s post here about selecting c-mount lenses. https://www.cloudyni...3/#entry8681636 If size and weight are a consideration, go with c-mount lenses. If you want a dual purpose handheld and afocal (TNVC adapter) lens , get a c-mount lens with 30.5mm thread. Otherwise there are more step rings required. A rats nest of different sizes. One day we will have afocal adapters to fit a variety of lenses. If cost is a factor, try finding adapters for lenses already owned. Shop KEH.com for used lenses. One attractive feature of SLR lenses is the image size exceeds the 2/3” and 1” formats of the c-mount lenses. If I read that tutorial correctly.

#8 The Ardent

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Posted 16 July 2018 - 07:49 PM

 

 

Once I get the parts in, should only take an afternoon to cobble it  20 units together.



#9 The Ardent

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Posted 16 July 2018 - 08:14 PM

C mount links

https://www.bhphotov...86?sts=hist-cat

https://www.thorlabs...ctgroup_id=1822

http://www.rmaelectronics.com/lenses/  (seems to have the best selection)

https://en.wikipedia.org/wiki/C_mount

https://www.ebay.com/bhp/c-mount-lens (I'm very suspicious of buying anything here)

https://www.schneide...y.aspx?CID=1344  ($$$$)

http://www.tamron-us...fixed_focal.php

https://computar.com/section/2/

https://www.ptgrey.com/camera-lenses



#10 Jeff Morgan

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Posted 17 July 2018 - 12:25 AM

 

 

 

Once I get the parts in, should only take an afternoon to cobble it  20 units together.

 

lol.gif

 

Then you'll make me register as a Vendor and all the fun will be gone.

 

Although the thought did cross my mind to order all six mirrors this vendor had available.


Edited by Jeff Morgan, 17 July 2018 - 12:26 AM.


#11 GeezerGazer

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Posted 17 July 2018 - 12:51 AM

Ray, your initial posts in this thread were really nicely presented and understandable.  waytogo.gif

 

Regarding camera lenses that are physically smaller for convenience at longer focal lengths, the 4/3 format lenses produced by Olympus and Panasonic/Leica since about 2010 are also a good choice.  They are expensive but they are very sleek, modern lenses of excellent quality that are also adaptable to C-mount.  Olympus now makes a 1.4x teleconverter for their pro series and MetaBones makes a .71x reducer that works extremely well with the lenses.  I know they can be manually focused but am not sure if they need the electric connection to the camera for aperture adjustments like most of the auto focus lenses for other formats.

 

And I agree with your assessment of the 3x afocal lens that can be screwed directly to the the Envis lens or applied with adapters to slide over the lens.  I usually screwed it to the Envis to reduce vignetting; and I press fit a filter cell to the front of it (Eddgie's recommendation) so I could add 58mm IR filters as a first surface.  The 3x is a little faster to add to the Envis than switching camera lenses.  And its coatings are optimized for the NVD.  But overall, I prefer my Nikon camera lenses which provide an equally bright image without the mechanical vignetting of the 3x and are less expensive to purchase used.  I have my 3x afocal lens listed for sale... because I seldom used it in preference to 2x, 4x and 5x camera lenses for different scales.  And, like you, I made sure all three camera lenses had the same filter threads.  But my preference is somewhat biased because of my use of the lenses for phonetography.  The full frame 35mm lenses provide a cropped image in NVDs, but they do not vignette, so there is full field illumination.


Edited by GeezerGazer, 17 July 2018 - 12:55 AM.


#12 Jeff Morgan

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Posted 27 July 2018 - 05:58 PM

My second eBay mirror arrived, the first having been poorly packaged and victim to the tender mercies of the USPS. Fortunately, I documented it and got a refund via eBay.

 

Just as well too, because I noticed something very much better! This is a slightly smaller JDS Uniphase laser bounce mirror (8" square), but it comes with a yoke mount frame. Thankfully, it this seller packed it professionally. My original idea of copying the old SkyWindow design where the mirror only tilts in one axis meant that the observer must reposition body and chair to move more than a few degrees in azimuth.

 

With two a two axis yoke, the mirror still tips forward and back for altitude coverage, but also tips right and left for azimuth coverage (via the hole in the yoke "handle"). Thus an entire hemisphere (180 degrees) is available without the observer having to reposition.

 

The simple yoke frame will also simplify the build. This one cost $40 more on eBay, but well worth the extra.

 

A couple of photos below. I had to put in a couple of extra plastic washers to get clearance for the yoke to swing past the mirror. The original unit also had three spring-loaded "collimation" bolts. I think the intended use was to set the yoke close to the desired bounce angle and use the acorn nuts on those bolts to fine-tune. I removed the springs and will shorten the bolts.

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#13 The Ardent

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Posted 12 August 2018 - 02:54 AM

This morning the skies cleared unexpectedly after a downpour. I used the Canon lens to view Perseids from my streetlight- lit, city backyard. None were visible by eye. 

 

Then ( for the first time ) I actually used this lens with a camera. I'm pleased with the result, considering it's a 1970's lens not made for astronomy. And I'm no imager. I'm very satisfied that the lens serves a dual purpose. That's value IMO. 

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#14 Tim M

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Posted 18 August 2018 - 10:57 PM

To to keep things simple I only use Canon FD mount lenses with a 55mm front filter. The front filter threads come in a variety of sizes. There are plenty of adapters out there, but for consistency I chose 55mm only. I have two 55 to 48mm step down rings to use 2" filters. I also have a couple of 55mm infrared filters. 

 

I just ordered a 55mm to 30.5 mm step down ring ($3) to attempt afocal with the Canon lenses. We'll see how that works. 

"55-30.5 for afocal with Canon lenes"?  Did you ever try this?  Are you saying to reverse-mount the FD lens to the NV (using the TNVC adapter)?  I've got a PVS-14 (and TNVC adapter and a few old FD lens), so my options are limited to afocal.

 

Thanks,

Tim



#15 Jeff Morgan

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Posted 08 October 2018 - 11:46 AM

 

 

 

Once I get the parts in, should only take an afternoon to cobble it  20 units together.

 

Waiting for the epoxy to dry on my carbon fiber dob project, thought I might get busy on this ...

 

Introducing Version 1.0 of the Seated NV Telephoto SkyScanner.

 

Basically, this is just a siderostat with an alt-alt mount (see January 1986 Sky & Telescope). Meaning, both axis move in altitude and are oriented at right angles to each other.

 

With this arrangement, the observer can cover 1/2 of the celestial sphere without moving the observing chair or the tripod. In practice, you do do a little better than 1/2 sky coverage until the mirror starts to show the observers head.

 

In addition to the first surface mirror on a yoke mount, the project uses a short Losmandy D plate, and Losmandy camera mount.

 

The device has three feet underneath for tabletop use, or it can be mounted to a tripod with standard 3/8 thread.

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#16 Jeff Morgan

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Posted 08 October 2018 - 11:49 AM

Unfortunately, Version 1.0 had some problems:

 

1) I did not allow for left/right mirror clearance with the bottom board when the mirror tips toward the observer. Meaning, as one approaches the Zenith, sky coverage left and right becomes limited.

 

2) The distance from the optical axis to the D plate is less than the distance from my eyeball to my chin. Meaning, only about 4” of travel adjustment on the D plate is possible before I hit my chin on the plate.

 

So, a little saw work and spacer was required. Introducing Version 2.0 of the Seated NV Telephoto SkyScanner.

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#17 Jeff Morgan

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Posted 08 October 2018 - 11:50 AM

Version 2.0 works very nicely. The views are rock-steady with no observer arm or neck fatigue. It is very relaxing to use!

 

The views of course are mirror reversed, but SkySafari easily compensates for this. Uranometria is a little trickier.

 

The green laser used for steering the mirror is too far away from the optical axis however. The mirror can only be tipped around 30 degrees left, beyond this the laser misses the mirror.

 

Version 2.5 will move the laser very close to the optical axis.


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#18 moshen

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Posted 10 October 2018 - 12:12 AM

Wow, this is a very interesting project.

I wonder what the reflectivity curve is for a kind of mirror like this in the near-IR.

 

Nice job!



#19 Jeff Morgan

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Posted 10 October 2018 - 01:33 AM

Wow, this is a very interesting project.

I wonder what the reflectivity curve is for a kind of mirror like this in the near-IR.

 

Nice job!

 

Thanks.

 

My guess is reflectivity falls off pretty fast past 750nm.

 

During the excesses of my youth I suffered a neck injury that seemed like nothing at the time. Some 30+ years later MRI's proved otherwise. Odd or prolonged neck angles just don't work for me anymore.

 

The concept might be handy for other folks starting to feel the bite of arthritis too.



#20 Jeff Morgan

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Posted 27 October 2018 - 11:48 PM

Third time is a charm - as in Version 3.0

 

I added an extension on to the riser that holds the NV eyepiece and drilled a 9/16" hole in it to mount the laser pointer closer to the telephoto lens. Most lasers are just under 9/16", so a little Scotch Tape around the laser barrel and it fits snug. Since most telephotos yield 5+ degrees, aiming the laser is not that critical, although it appeared to be dead center with a slight rotation of the NV device.

 

This allowed me to get rid of that funky looking laser stalk, much cleaner look.

 

Also, the 1/4-20 hand knob that connects to the NV eyepiece is captive in the Losmandy design. But once I put a riser on the camera mount, the knob was no longer constrained and could drop free. Which means it eventually gets lost or misplaced. So, I put a t-nut on the bottom of the mount (where the old laser stalk was located) and the knob just threads into it for safe keeping.

 

I had an hour of good darkness before moonrise and gave it a spin. Success! So easy and relaxing to use! Zero fatigue. Rock steady too. Very faint stars are possible when the view is this steady.

 

Of course, it did take me half an hour or so to remember how to star hop - no DSC's on this puppy! It helps to take the h-alpha filter off of the camera lens for star hopping (technique only).

 

Here is the finished version, and a couple of shots I took tonight with my iPhone X (135mm and 50mm). These are unguided so I limited exposures to 10 seconds, and flipped the photos horizontally to undo the mirror image:

 

 

 

 

 

 

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#21 Eddgie

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Posted 28 October 2018 - 07:56 AM

Very nice Jeff!   



#22 avid_dk

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Posted 28 October 2018 - 10:34 AM

Wouldn't it be great if Jeff's great work could be transferred to it own thread with an appropriate title so it doesn't get lost in the vastness of CN. Actually, there are two great threads here that need to be separated and protected from disappearing.  JMHO

 

My other thought was that I never anticipated that delving more deeply into astronomy was going to require an entire woodworking setup.  That is the definition of an unintended consequence.  


Edited by avid_dk, 28 October 2018 - 11:27 AM.


#23 Jeff Morgan

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Posted 28 October 2018 - 02:49 PM

Very nice Jeff!   

 

Thanks!

 

Now that it works, it's time to grab that Nikon ED lens you have been so excited about. The scale should be just about what I am looking for. For example, the Elephant trunk it too large at 500mm, and yet too small at 135mm.

 

In fact, my impression of 135mm is that it is a "tweener". A 50, 85 or 100, and 185 might be just right ...


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#24 Jeff Morgan

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Posted 28 October 2018 - 02:59 PM

Wouldn't it be great if Jeff's great work could be transferred to it own thread with an appropriate title so it doesn't get lost in the vastness of CN. Actually, there are two great threads here that need to be separated and protected from disappearing.  JMHO

 

My other thought was that I never anticipated that delving more deeply into astronomy was going to require an entire woodworking setup.  That is the definition of an unintended consequence.  

 

Actually nothing fancy there. It's nice to have things like table saws and drill presses, but if could all be done with a $15 hand saw and a drill. You could even use nails and screws, but wood dowels and glue are better.

 

The wood was just scrap pieces I had laying around.

 

Even construction grade plywood would be fine for a project like this. Make a mistake? Just cut it off, sand it down, glue a new piece on. Once it does what you want, you can do wonders with a little wood filler, sandpaper, and paint wink.gif

 

I think I'll make this one Camo ...

 

One more picture, NV eyepiece and 135mm telephoto:

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#25 avid_dk

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Posted 28 October 2018 - 03:32 PM

Actually nothing fancy there. It's nice to have things like table saws and drill presses, but if could all be done with a $15 hand saw and a drill. You could even use nails and screws, but wood dowels and glue are better.

 

The wood was just scrap pieces I had laying around.

 

Even construction grade plywood would be fine for a project like this. Make a mistake? Just cut it off, sand it down, glue a new piece on. Once it does what you want, you can do wonders with a little wood filler, sandpaper, and paint wink.gif

 

 

The other astro project on hold is a 12 or 16"  dob.  My late father could do this kind of stuff with a hand saw and a drill.  Me, not so much.  




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